DRAFT ENVIRONMENTAL ASSESSMENT & ANTICIPATED FINDING OF NO SIGNIFICANT IMPACT, CALTECH SUBMILLIMETER OBSERVATORY DECOMMISSIONING PREPARED FOR: California Institute of Technology PREPARED BY: JULY 2021 DEA/AFONSI, Caltech Submillimeter Observatory Decommissioning Table of Contents TABLE OF CONTENTS CHAPTER 1: INTRODUCTION ............................................................................................ 1-1 OVERVIEW OF THE PROPOSED ACTION ................................................................................ 1-4 PURPOSE OF THE PROPOSED ACTION ................................................................................... 1-4 NEED FOR THE PROPOSED ACTION ...................................................................................... 1-5 PURPOSE OF THIS ENVIRONMENTAL ASSESSMENT .............................................................. 1-5 PERMITS AND APPROVALS ................................................................................................... 1-5 ORGANIZATION OF THE ENVIRONMENTAL ASSESSMENT ..................................................... 1-6 CHAPTER 2: DESCRIPTION OF PROPOSED ACTION.................................................. 2-1 DESCRIPTION OF THE PROPOSED ACTION ............................................................................ 2-1 2.1.1 Description of Existing Facilities ............................................................................................ 2-1 2.1.2 CSO Deconstruction and Removal Methodology ................................................................... 2-3 2.1.3 Site Restoration Methodology ............................................................................................... 2-19 2.1.4 Funding of Future Shared Infrastructure Removal ................................................................ 2-23 2.1.5 Restoration Effectiveness Monitoring ................................................................................... 2-25 PRELIMINARY SCHEDULE FOR THE PROPOSED ACTION ..................................................... 2-25 PROJECT BUDGET .............................................................................................................. 2-26 CHAPTER 3: PROJECT ALTERNATIVES ......................................................................... 3-1 FRAMEWORK FOR CONSIDERATION OF ALTERNATIVES ....................................................... 3-1 IDENTIFICATION OF FEASIBLE ALTERNATIVES .................................................................... 3-2 ALTERNATIVES FOR DETAILED CONSIDERATION ................................................................. 3-3 3.3.1 ALT-1: No Action ................................................................................................................... 3-3 3.3.2 ALT-2: Complete Facility and Infrastructure Removal with Full Restoration ........................ 3-3 3.3.3 ALT-3: Complete Facility and Infrastructure Removal with Moderate Restoration ............... 3-4 3.3.4 ALT-4: Facility Removal, Infrastructure Capping, and Moderate Restoration ....................... 3-6 ALTERNATIVES CONSIDERED BUT REJECTED .................................................................... 3-10 3.4.1 Reduced Scale Alternative ..................................................................................................... 3-10 3.4.2 Delayed Action Alternative ................................................................................................... 3-10 3.4.3 Alternative Location .............................................................................................................. 3-11 CHAPTER 4: EXISTING ENVIRONMENT, POTENTIAL IMPACTS, AND MITIGATION ................................................................................................................ 4-1 ARCHAEOLOGY ................................................................................................................... 4-1 4.1.1 Context ..................................................................................................................................... 4-1 4.1.2 Prior Studies ............................................................................................................................ 4-4 4.1.3 Fieldwork and Findings ........................................................................................................... 4-8 4.1.4 Potential Impacts ................................................................................................................... 4-10 4.1.5 Mitigation Measures .............................................................................................................. 4-10 CULTURAL IMPACT ASSESSMENT ...................................................................................... 4-10 4.2.1 Context ................................................................................................................................... 4-10 Page i DEA/AFONSI, Caltech Submillimeter Observatory Decommissioning Table of Contents 4.2.2 Cultural Overview ................................................................................................................. 4-11 4.2.3 Consultation ........................................................................................................................... 4-12 4.2.4 Potential Impacts ................................................................................................................... 4-16 4.2.5 Mitigation Measures .............................................................................................................. 4-18 BIOLOGY ........................................................................................................................... 4-18 4.3.1 Context ................................................................................................................................... 4-18 4.3.2 Existing Conditions ............................................................................................................... 4-18 4.3.3 Potential Impacts ................................................................................................................... 4-23 4.3.4 Mitigation Measures .............................................................................................................. 4-25 VISUAL AND AESTHETIC RESOURCES ................................................................................ 4-25 4.4.1 Existing Conditions ............................................................................................................... 4-26 4.4.2 Potential Impacts ................................................................................................................... 4-27 4.4.3 Mitigation Measures .............................................................................................................. 4-27 GEOLOGY AND TOPOGRAPHY ............................................................................................ 4-29 4.5.1 Context ................................................................................................................................... 4-29 4.5.2 Existing Conditions ............................................................................................................... 4-33 4.5.3 Potential Impacts ................................................................................................................... 4-34 4.5.4 Mitigation Measures .............................................................................................................. 4-34 HYDROLOGY ..................................................................................................................... 4-34 4.6.1 Existing Conditions ............................................................................................................... 4-35 4.6.2 Potential Impacts ................................................................................................................... 4-49 4.6.3 Mitigation Measures .............................................................................................................. 4-54 SOLID AND HAZARDOUS WASTE ....................................................................................... 4-54 4.7.1 Existing Conditions ............................................................................................................... 4-54 4.7.2 Potential Impacts ................................................................................................................... 4-56 4.7.3 Mitigation Measures .............................................................................................................. 4-56 TRAFFIC ............................................................................................................................ 4-57 4.8.1 Existing Conditions ............................................................................................................... 4-57 4.8.2 Potential Impacts ................................................................................................................... 4-59 4.8.3 Mitigation Measures .............................................................................................................. 4-61 NOISE ................................................................................................................................ 4-62 4.9.1 Context ................................................................................................................................... 4-62 4.9.2 Existing Conditions ..............................................................................................................